1. Field of the Invention
The present invention relates to a developing apparatus for a printer to be built in a printing apparatus, facsimile, a copying machine, or the like and in particular, to a developing apparatus using a liquid developer.
2. Description of the Related Art
FIG. 3 shows a conventional example. In FIG. 3, the reference numeral 101 denotes an endless belt type photosensitive body. Outside of this belt type photosensitive body 101, i.e., below the belt type photosensitive body 101 in FIG. 3(a), there are provided a development roller 102 and a squeeze roller 103.
The development roller 102 makes visible, i.e., develops an electrostatic latent image on the belt type photosensitive body 101 and is arranged with its rotary surface at a predetermined distance from the surface of the belt type photosensitive body 101 having the electrostatic latent image. The squeeze roller 103 serves to remove a portion of liquid developer remaining on the belt type photosensitive body 101. For this, the squeeze roller 103 is located at the downstream of the development roller 102 along the travelling surface of the belt type photosensitive body 101.
The reference numeral 121 denotes a first backup roller arranged against the development roller 102 via the belt type photosensitive body 101. The reference numeral 122 denotes a second backup roller arranged against the squeeze roller 103 via the belt type photosensitive body 101.
Beside the development roller 102, there is provided with a developer supply 105 for supplying a liquid developer to the development roller 102. Beside the squeeze roller 103, there is provided a cleaning blade 106 for removing a liquid developer from the squeeze roller 103.
The development roller 102, the developer supply 105, the squeeze roller 103, and the cleaning blade 106 are all contained in a developing apparatus casing 130. In a developing mode, these components are set as a unitary block at an advanced position toward the belt type photosensitive body 101, and in a development stop mode these components are set as a unitary block at a recessed position
The squeeze roller 103 removes liquid developer remaining on the belt type photosensitive body 101 and makes the developed visible image into a film state. For this, the squeeze roller 103 rotates against the second backup roller 122 while sandwiching the belt type photosensitive body 101. Actually, the squeeze roller 103 is in a pressed state against the second backup roller 122 with a predetermined pressure.
In the aforementioned conventional example, the squeeze roller 103 should be pressed against the second backup roller 122, so as to evenly press the entire width of the belt type photosensitive body 101. In case when the diameter of the squeeze roller 103 is smaller than the diameter of the backup roller 122, there is a problem that the squeeze roller 103 is easily deflected. In order to prevent this, in the aforementioned conventional example, the diameter of the squeeze roller 103 is made greater.
However, in this case, if the diameter of the squeeze roller is made greater while using the same material and the same pressure, the nip width d (in FIG. 3(b)) formed on the abutment surface between the second backup roller 122 and the squeeze roller 103 becomes greater and the abutment pressure per a unit area becomes smaller. This causes a problem not only in making a visible image into a film state but also in removing remaining liquid developer because the portion from where the remaining liquid developer is to be removed has a concave form.
On the other hand, in order to eliminate the problem of FIG. 3, Japanese Patent Publication 9-171321 discloses an arrangement in which an auxiliary roller having a small width is provided at a central portion of the squeeze roller 103 for correcting the deflection.
However, after a long period of use, the central portion of the squeeze roller 103 is physically deformed and it becomes difficult for a visible image to be made into a uniform film state. Furthermore, there arises a problem that the squeeze roller 103 cannot have a long service life.
It is therefore an object of the present invention to provide a developing apparatus capable of smoothly making into a visible image an electrostatic latent image on the belt type photosensitive body, making the visible image into a uniform film state, effectively removing remaining liquid developer, and having a long service life.
In order to achieve the aforementioned object, the present invention provides a developing apparatus for a printer, the apparatus comprising a liquid developer supply unit for supplying a liquid developer to a predetermined electrostatic latent image on a belt type photosensitive body and a liquid component removing unit arranged at the downstream of the liquid developer supply unit so as to remove a liquid component from the liquid developer attached to the belt type photosensitive body by the liquid developer supply unit, wherein the liquid component removing unit includes a squeeze roller arranged at the liquid developer side of the belt type photosensitive body so as to remove a liquid component from the liquid developer attached to the belt type photosensitive body and a liquid component removing auxiliary roller which is in abutment with the squeeze roller via the belt type photosensitive body. And the liquid component removing auxiliary roller has a diameter greater than a diameter of the squeeze roller and a length almost identical to a length of the squeeze roller.
Accordingly, it is possible to smoothly develop the electrostatic latent image on the belt type photosensitive body. Furthermore, the liquid component removing unit can effectively remove a remaining liquid developer and an unnecessary liquid component from the belt type photosensitive body. Simultaneously with this, the visible image developed by the liquid developer supply unit is smoothly made into a film state by cooperation of the liquid component removing auxiliary roller and the squeeze roller.
Since the liquid component removing auxiliary roller has a diameter greater than that of the squeeze roller and a length almost identical to that of the squeeze roller, it is possible to almost completely eliminate the problem of curving (bending) of the squeeze roller in the conventional example, disturbing the process of making the visible image into a film state. Thus, it is possible to continue the development process in a stable state for a long period of time.
The liquid component removing unit may further include an SQ support roller which is in abutment with the squeeze roller with a predetermined pressure and removes a liquid developer from the squeeze roller.
Since the rotation of the squeeze roller is entirely supported by the SQ support roller, the rotation of the squeeze roller is made more stable. Moreover, the entire surface of the squeeze roller is evenly supported and accordingly, it is possible to completely eliminate the problem of abrasion or deformation of the center portion. This brings out operation stability and durability.
Here, the SQ support roller may have a diameter greater than that of the squeeze roller. This further increases the operation stability of the squeeze roller and durability against vibration or the like.
The liquid component removing auxiliary roller, the squeeze roller, and the SQ support roller may have rotation centers set on a single line.
Accordingly, when the squeeze roller is pressed against the liquid component removing auxiliary roller, the pressure can be effectively transmitted.
Here, the squeeze roller and the SQ support roller may be constituted so as to be movable as a unitary block apart from the belt type photosensitive body. With this configuration, it is possible to smoothly switch the developing apparatus between a development mode and a non-development mode.
Moreover, the squeeze roller may be constituted so as to be rotated in a reverse direction at a predetermined timing. This enables to rapidly and completely remove the remaining liquid developer and unnecessary liquid component from the belt type photosensitive body, which in turn enables to obtain a high quality development including the film state of the visible image.